The present proposal is designed to provide the applicant, who has a strong background in classical mechanical engineering, with knowledge and experience in the emerging fields of photomedicine and biomedical optics required to launch a successful independent research career in biomedical engineering. The proposed studies investigate the appropriate use of yellow light emitted by pulsed dye lasers in combination with short cryogen spurts to improve the therapeutic outcome of port wine stains (PWS) in infants and young children. PWS are a congenital, progressive vascular malformation of the dermis that occurs in approximately 0.7% of children (approximately 1,500,000 individuals in the United States and 32 million people worldwide). unfortunately, two major problems prevent the use of high laser dosages required to permanently remove PWS vessels in infants and young children, namely: (A) the efficiency of cryogen spray cooling (CSC) nozzles is insufficient to provide the necessary epidermal protection; and (B) all patients are treated with CSC and laser light doses based on clinical judgment of the physician, without considering individual variations in epidermal melanin concentration and PWS depth and thickness. To address these problems, four studies are proposed: (1) design of new cryogen atomizing nozzles to maximize CSC efficiency; (2) development of new heat diffusion, light absorption, and thermal tissue damage numerical models to evaluate instantaneous skin temperature profiles and epidermal and PWS damage; (3) optimization of CSC and laser parameters to deliver higher energy to the PWS while preserving the epidermis; and (4) incorporation of visible reflectance spectroscopy (V.S.) and pulsed photothermal radiometry (PER.) measurements on PWS patients into numerical model to predict therapeutic outcome based, on realistic clinical data. The results of the proposed studies will greatly enhance current PWS laser therapy, and provide a much more effective and safer approach to clinical management of infants and young children. The support provided by a OR. award will provide the applicant with the protected period to conduct high-quality research under the guidance of his mentor while having full access to the outstanding facilities available at the Beckman Laser Institute (BLS) and School of Engineering (SOE) at The University of California, Irvine (UCI). Additionally, the applicant will receive instruction through formal coursework and conference participation, acquire new knowledge, such as transport of light in living tissues, and develop new skills, such as the application of clinical optoelectronic and laser equipment. Ultimately, the combination of research, coursework, and clinic experience, will provide the applicant with the preparation to launch an independent and successful research career in biomedical engineering.